EP 0 811 443 B1 has made known a tangential thread-rolling head in which two thread-rolling dies are rotatably supported by two fork-shaped rolling head arms. The thread-rolling dies have to be in a certain position to each other at the beginning of a thread-rolling procedure and during the rolling procedure. For this purpose, a synchronized gearbox is disposed between the tangential rolling dies. The axle of each rolling die has arranged thereon a pinion which, on its front face, has a pair of diametrically opposed jaws which get into engagement with complementary jaws of the thread-rolling die. This transfers a rotational motion to the thread-rolling die from the pinion. The pinion, in turn, interengages with a gear where the two gears interengage with a central gear in order to ensure the uniformity of the rotational motion for the two thread-rolling dies.
It is understood that the thread-rolling dies are in a predetermined axial position towards each other. Typically, the thread-rolling dies cause a front face to bear against a stop which is defined by a forked portion of the fork-shaped arms. A particular metallic disk, e.g. made of copper, defines a stop surface which additionally causes a relatively low friction. To make the thread-rolling die bear against the stop, it is known to locate it axially by means of a bushing which is mounted on the axle for the thread-rolling die and the pinion. The bushing, in turn, is axially located by a further bushing which supports the gear meshing with the pinion. This bushing is pressed against a fixed contact surface of the rolling head arm by means of a screw.
As becomes apparent from this description such a procedure only helps to provide for a single adjustment of the axial position of the thread-rolling die. If it is to be changed the length of the second bushing would have to be reduced by grinding. The description further makes it evident that the tolerances will possibly be added up because of an interaction between a plurality of individual parts, which detracts from the accuracy of the axial position or axial rolling die clearance. Thus, for example, the contacting disk can wear down, which results in a change to the axial position of the thread-rolling die. The known means are unable to provide a compensation. However, the accuracy of the axial position or axial clearance of the rolling dies is of great significance for the accuracy of the thread to be produced by the thread-rolling dies.